The present invention relates to bar code scanners. More particularly, the invention relates to methods and apparatus for collecting and recording time and mirror position information during bar code scans.
Bar code scanners are presently used in numerous applications, and help to increase efficiency and accuracy wherever they are used. The use of bar code scanners in retail transactions decreases the time required to enter a transaction, and decreases the chance of an error during manual entry of data. Properly used, bar code scanners allow for increased efficiency in the use of labor, increased customer satisfaction due to reductions in waiting time and incorrect charges, and an improved quality of operation that comes from the reduction of pricing errors. Moreover, bar code scanning allows for instant, accurate updating of inventory, making for a greatly increased efficiency of operation.
Present-day bar code scanners are subject to fairly frequent failed scans. This requires that the item be rescanned, or that the item code be manually entered. This slows the scanning operation and impedes its efficiency.
In order to improve scanning efficiency and decrease the number of failed scans, modern-day high performance bar code scanners collect partial scans of bar codes as well as complete ones. When only partial scans or bar code fragments are available, an attempt is made to construct a valid bar code from them.
In bar code scanners of the present state of the art, only numerical information from the bar code itself is collected. In other words, present-day scanners are unable to gather information about the position of the bar code or the speed or timing of the scan. The information that is available for reconstruction of partial scans is therefore limited, reducing the number of successful bar code reconstructions from partial scans.
Bar code scanners typically include a laser beam directed by mirrors and/or lenses which is aimed at an area or volume being scanned. Light from the laser is collected from this area or volume and directed to a photodetector using a similar means. The signal from the photodetector is analyzed by a computing device which attempts to produce valid bar codes from the incoming signals. By way of example, at the supermarket checkout station, the checker passes each item to be purchased past a scanner such as the NCR 7875 model scanner.
It would greatly enhance the ability of the bar code scanner to capture information and reconstruct information from a partial scan, if the scanner could capture the time at which the bar code fragment was received, as well as the angle of the rotating mirror assembly at the time the data was collected. This would greatly increase the available information from which a complete bar code could be constructed. For example, probable location of the label could be recovered, as well as speed and direction of travel of the label, which would greatly improve the efficiency of the scanning process.
Moreover, numerous possibilities exist for ambiguity and confusion during the scanning of a bar code. For example, if two items come within the field of view of the scanner at the same time, it is not possible to scan them both. Rather, it is much more likely that the scanner will be unable to resolve the information from the two codes and the scan will fail. The addition of position and timing information would increase the likelihood that the two objects could both be distinguished and be successfully recognized.
There exists, therefore, a substantial need in the art for a bar code scanner which collects and stores timing and mirror angle or position information during a scan, for use in increasing the likelihood of success of the scan.
The present invention advantageously recognizes and addresses these and other needs as more fully described below. A bar code scanner according to one embodiment of the present invention includes a laser for producing light which is reflected from a bar code during a scan. The light is transmitted through an optical assembly including a rotating portion, or spinner, driven by a motor. The direction and location of incidence of the light depends on the angular position of the spinner. Associated with the motor is a Hall effect or other device for producing a pulse or pulses as the spinner rotates. A fixed number of pulses will occur for each rotation of the motor. The occurrence of each pulse correlates with a position of the motor. For example, two pulses may occur for each rotation. Thus, it is known that every other pulse the motor returns to a known reference position. A precise clock count can by synched off the pulse for the return to the reference position. From this time count and knowledge of the speed of rotation, a processor can readily determine the angular position of the motor at the time of an occurrence of interest, typically a scan or partial scan of a bar code.
By reconstructing in time and space the probable location of a bar code label at the time scanned, a large number of advantages may be achieved. For example, more than one bar code label can be read at the same time, whether or not the two labels are on the same item or two different items, and even if both have the same bar code data. The time and space data will allow discrimination between two items of the same kind scanned in rapid succession or even substantially simultaneously from a rapidly occurring double read of the same item.
Reconstruction of the location of a bar code label in space and time allows the determination of the speed and direction of the label as it is passed over the scanner. This allows the scanner to be programmed to give feedback to a cashier to assist in self-training to improve the efficiency of utilization of the scanner. The time and space data also makes it possible to capture improved first pass read metrics to allow a store manager to determine which cashiers are most efficient and which need further training.
Additionally, improved checkout security and checkout accuracy are provided. The probability of a false code being reconstructed out of partial reads of two different labels is significantly reduced. Labels which leave the scan zone and are returned can be recognized and ignored. For example, if an item is moved right to left across the scanner for a good read and is then moved left to right into the scan zone and then back to the left out of the scan zone, the second time the label is scanned can be safely ignored. Thus, the present approach can be used to prevent double reading in this and other circumstances. Further, the delay between reads of items can be reduced or eliminated.
Further, data received through multiple filtering circuits can be advantageously collected and correlated. Data received from certain angles or areas of the scan zone can be ignored if corresponding data is not detected in other portions of the scan zone to prevent misreads, such as belt reads. Filtering modes for certain areas of the scan zone can be selectively changed. Thus, by recording time and position data a host of substantial improvements can be achieved.
Additional features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.